Joseph Despres

Germanium ion implantation efficiency improvement with use of germanium tetrafluoride

Ion implantation of germanium in silicon wafers is often troubled by reduced ion source life due to use of germanium tetrafluoride (GeF₄) as a source material. The problem is mainly due to tungsten re-deposition, a result of a fluorine-induced halogen cycle initiated within the ion source. The halogen cycle is particularly pronounced in the case of GeF₄ by easy fragmentation of the molecule, as well as low utilization of germanium due to wide isotopic distribution of natural abundance GeF₄. Through isotopic enrichment of ⁷²GeF₄, benefits such as enhanced ion implantation beam current, lower gas flow, and longer source life can be achieved versus natural GeF₄. Additional benefits can be realized when using mixtures of GeF₄ with hydrogen (H₂). Data are presented that show the effect of H₂ content on beam current as well as on tungsten transport. Lastly, thermodynamics and stability results are presented for a single cylinder mixture of GeF₄ with H₂.

Comparison of SAGS I vs. SAGS II delivery systems in emerging implantation technologies

The International Fire Code has classified Subatmospheric Gas Delivery Systems (SAGS) technologies into two main categories: SAGS Type I and SAGS Type II systems. SAGS Type I delivery systems both store and deliver gases at subatmospheric pressures. An example of this technology is ATMI’s Safe Delivery Source (SDS®) adsorbent based cylinder. SAGS Type II delivery systems store fluids at high pressure and utilize mechanical devices internal to the cylinder to deliver the gas at subatmospheric pressures. Typical mechanical devices used to enable subatmospheric delivery are either set point regulators or mechanical capillary based systems. This paper focuses on how these delivery systems perform against the unique requirements of traditional beam line ion implantation as well as solar and flat panel applications. Specifically, data are provided showing the capability of these systems with respect to flow rate, residual gas left within the cylinder, and cylinder end-point flow and delivery pressure dynamics.

Atomic layer deposition of boron-containing films using B2F4

Ultrathin and conformal boron-containing atomic layer deposition (ALD) films could be used as a shallow dopant source for advanced transistor structures in microelectronics manufacturing. With this application in mind, diboron tetrafluoride (B2F4) was explored as an ALD precursor for the deposition of boron containing films. Density functional theory simulations for nucleation on silicon (100) surfaces indicated better reactivity of B2F4 in comparison to BF3. Quartz crystal microbalance experiments exhibited growth using either B2F4-H2O for B2O3 ALD, or B2F4-disilane (Si2H6) for B ALD, but in both cases, the initial growth per cycle was quite low (≤0.2 A/cycle) and decreased to near zero growth after 8–30 ALD cycles. However, alternating between B2F4-H2O and trimethyl aluminum (TMA)-H2O ALD cycles resulted in sustained growth at ∼0.65 A/cycle, suggesting that the dense –OH surface termination produced by the TMA-H2O combination enhances the uptake of B2F4 precursor. The resultant boron containing films we...

Gas cylinder release rate testing and analysis

There are varying cylinder technologies employed for the storage of gases, each resulting in a potentially different hazard level to the surroundings in the event of a gas release. Subatmospheric Gas delivery Systems Type I (SAGS I) store and deliver gases subatmospherically, while Subatmospheric Gas delivery Systems Type II (SAGS II) deliver gases subatmospherically, but store them at high pressure. Standard high pressure gas cylinders store and deliver their contents at high pressure. Due to the differences in these cylinder technologies, release rates in the event of a leak or internal component failure, can vary significantly. This paper details the experimental and theoretical results of different Arsine (AsH3) gas cylinder release scenarios. For the SAGS II experimental analysis, Fourier Transform Infrared Spectroscopy (FTIR) was used to determine the spatial concentration profiles when a surrogate gas, CF4, was released via a simulated leak within an ion implanter. Various SAGS I and SAGS II cylind...

Source and beam performance improvement for carbon implantation with carbon monoxide (CO) gas

Carbon co-implantation has been widely adopted for better Ultra-Shallow Junction formation in the fabrication of advanced semiconductor devices. Currently, carbon dioxide (CO2) is the primary feed gas for carbon implantation. The primary disadvantage of CO2 is the high oxygen content, which causes significant oxidation of the implant source components resulting in rapid degradation of the source performance. Usually the C+ beam starts to degrade quickly while running continuously with carbon dioxide. Also, some other species’ implants, especially boron, are significantly affected after a short duration of CO2 usage. Carbon monoxide (CO) is described here as an alternative carbon source material to CO2. In our testing, CO has demonstrated significant improvements compared to CO2 for both source life and beam performance. Additionally, this paper describes a subatmospheric delivery option for CO. The cylinder package with reliability information is provided.Carbon co-implantation has been widely adopted for better Ultra-Shallow Junction formation in the fabrication of advanced semiconductor devices. Currently, carbon dioxide (CO2) is the primary feed gas for carbon implantation. The primary disadvantage of CO2 is the high oxygen content, which causes significant oxidation of the implant source components resulting in rapid degradation of the source performance. Usually the C+ beam starts to degrade quickly while running continuously with carbon dioxide. Also, some other species’ implants, especially boron, are significantly affected after a short duration of CO2 usage. Carbon monoxide (CO) is described here as an alternative carbon source material to CO2. In our testing, CO has demonstrated significant improvements compared to CO2 for both source life and beam performance. Additionally, this paper describes a subatmospheric delivery option for CO. The cylinder package with reliability information is provided.

Hydrogen Selenide (H2Se) Dopant Gas for Selenium Implantation

With the continued scaling of semiconductor devices, controlling contact resistance becomes more and more challenging. Selenium (Se) ion implantation is noted in the literatures to effectively reduce contact resistance in NMOS transistors by lowering the electron Schottky barrier height (SBH). A suitable selenium source feed material is required and can be in solid form, such as selenium oxide (e.g. SeO2), or in gas form, such as hydrogen selenide (H2Se). Solid source materials in general suffer from relatively longer setup times and concern of re-deposition of the dopant, whereas hydrogen selenide gas stored at high pressure poses safety and handling issues. In this paper, we present performance and usage data associated with a subatmospheric source of H2Se, including beam setup, Se+ beam current, beam stability, and source conditions. Material properties, as well as the subatmospheric delivery source are also described.

Carbon Implantation Performance Improvement by Mixing Carbon Monoxide (CO) with Carbonyl Fluoride (COF2) and Carbon Dioxide (CO2)

Co-implantation of impurities such as carbon (C) has been proven to effectively reduce Transient Enhanced Diffusion (TED) of boron during annealing, enabling the formation of high-quality ultra-shallow junctions - a requirement for advanced-node semiconductor devices. Carbon dioxide (CO2) is traditionally used as the feed gas in implant tools for carbon implantation. Recently, carbon monoxide (CO) has been widely adopted as a replacement to CO2 due to its lower oxygen content. To further improve the carbon implant performance, a mixture of CO, carbonyl fluoride (COF2), and CO2 is studied and reported in this paper. The effects of the additional fluorine and extra oxygen content from COF2 or CO2 are investigated. Our experiments show that with the right balance and mixture level of COF2 and CO2, the carbon mixture can achieve improvements in key implant tool performance parameters, such as beam current and source life. Additionally, the CO/COF2/CO2 mixture stability is studied, and a safe delivery package is described.

Investigation of Boron Gas Mixtures for Beamline Implant

Beamline implant productivity challenges associated with high dose p-type boron doping have been well documented. Recently, BF3/H2 mixtures were shown to be an effective alternative to BF3 in enabling implant tool productivity improvements through the extension of ion source life - which is accomplished with hydrogens ability to interrupt the halogen cycle that otherwise is responsible for depositing tungsten on sensitive ion source components [1]. Presented here are additional studies of boron mixtures with the goal of further improving ion source performance. Specific mixtures tested include various compositions of BF3/B2H6 as well as BF3/B2H6/H2. Beam current and mixture stability are examined, and ion source condition observations are provided.

Utilization of SAGS Type 1 delivery systems in novel doping applications

The advent of new technologies is driving the emergence of alternative doping methods. For instance, plasma doping is potentially a critical enabler for three-dimensional (3D) devices in the integrated circuit (IC) market, requiring flow rates much higher than those of traditional planar structures. Unlike traditional beam-line ion implantation, dopants are typically not introduced from an on-board gas box within the tool; rather they are distributed from a remote gas delivery system. This is possible given that the gas delivery system is held at the same potential as the tool and there is no high voltage gap to overcome. Similarities exist in other markets such as solar, flat panel display, and power electronics, in terms of needing to deliver high gas flows from a remote delivery source. This requirement poses significant hurdles in terms of process safety, installation considerations, and the ability to enable high gas conductance through proper flow component selection. This paper details how each of these factors affects the performance of the system and the ability to achieve the required process flow rates. Theoretical flow modeling is used to estimate overall system conductance and gas utilization and these results are compared to empirical data to show that system attributes can be predicted. This capability coupled with a gas delivery cabinet that is designed to enable the performance and safety of SAGS Type1 delivery systems, provides a robust solution to material delivery needs for novel doping applications.